The present invention relates to a cellular phone comprising a central processing unit (CPU).
A hand-held terminal or mobile terminal, for switching the frequency of a clock signal delivered from the side of an application program, is disclosed in JP-A NO. 73237/1999 (Heisei 11).
Further, in JP-A No. 148475/2000, there is disclosed a computer for a mobile unit, capable of switching a clock frequency to a high-speed mode frequency higher than a normal frequency when conditions, such as power source voltage, ambient temperature, and so forth, are satisfied.
In the case of the conventional technology described above, speed control of a clock signal has been implemented by an application program or has been dependent on the conditions such as power source voltage, ambient temperature, and so forth, so that there is no room for interposition of the will of a user in switching the speed of the clock signal. Further, if the CPU is driven at a high frequency, there has been a tendency toward an increase in current consumption although a processing speed is enhanced. With a cellular phone, in particular, since its battery capacity is small, there has been a risk of premature depletion of the battery capacity occurring when the clock signal has been automatically switched over to the high-speed side without knowledge of the user.